Linux Tweaks, HowTo's and Reviews

Edit: Oct. 2, 2010 - I've written a new post that shows a bash one-liner command that will remove the old kernels from your system in one step. You can check it out here.

If you've been using Ubuntu Linux for a while, then you probably have a number of Linux kernel updates that have been installed on your system. (I've got a total of 3 kernels in my Karmic system already.) In all likelihood, these updates get installed and you boot into the latest kernel, never to use the older kernels again. But these old kernels are still hanging around on your system, cluttering up your grub boot screen and taking up space on your hard drive.

There have been attempts made to create an automatic tool to clean these up for you along with much discussion on the Ubuntu Forums, but so far there's nothing officially in the repositories.

In the past, I've gone into Synaptic and searched for the older kernels and related packages and manually marked them for removal. This method works fine, but the search process is a little slow in Synaptic and you have to run a few searches to catch all of the packages to remove. I decided to come up with a way to do this from the terminal and hopefully save some time. The commands I'm going to use can be a bit daunting, so just copy and paste.

Warning

Don't follow this process unless you're sure you don't need to boot into the older kernels. If you're not sure, just leave things alone. Also, it is possible to remove all of the kernels from your system and make it unbootable. I suggest leaving the latest kernel and one version previous to that. You can find out the kernel version that you're currently running with

uname -r

Find and remove old kernels

The first step is to figure out what kernels are installed. The following command will do the job.

ls /boot | grep vmlinuz | cut -d'-' -f2,3

Your result should look something like this.

2.6.28-15
2.6.28-16
2.6.28-17

This is the list of kernels installed on your system. Now you want to find out which packages are installed relative to the kernel you want to remove. For my example I'm going to remove the oldest one, 2.6.28-15.

That's it. You've removed an old kernel and related packages. Now you can keep your system as clean as it is right after you install Ubuntu. The commands are a bit complex, so maybe I'll write up a bash script when I have some time. Proceed with caution!

Zach - Wow, that's one monster of a command! That one is going to take a while to digest. It looks like the uname -r | sed part of the command filters out the current kernel and then only the older kernels are fed into the apt-get purge command.

I might suggest removing the -y from the final portion of the command to run apt-get interactively.

Zach - Another nice tip. If I comment the lines
"^linux-image.*";
"^linux-restricted-modules.*";
"^linux-ubuntu-modules-.*";
would the old kernels be removed automatically, or would I have to runsudo apt-get autoremove